Unraveling the role of supersaturation in shaping 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) crystal via mechanistic growth model

Understanding and controlling the crystal morphology of energetic materials is crucial to optimize their performances. Supersaturation is a key factor influencing crystal growth kinetics and thermodynamics, and plays a critical role in morphology regulation. Herein, we employ a mechanistic growth model to investigate the morphology evolution of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) crystals under varying supersaturation in dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP) and dimethylformamide (DMF). By combining periodic bond chain analysis, edge energy calculations, and estimates of critical supersaturation for 2D nucleation, we find that facet-dependent 2D nucleation threshold enhances the growth anisotropy and drives the morphology change. At moderate supersaturation, as certain facets initiate 2D nucleation earlier, anisotropic growth is enhanced, leading to an increase in aspect ratio. At higher supersaturation, 2D nucleation dominates across multiple facets, reducing anisotropy and causing a slight decrease in aspect ratio. The strong π–π stacking along the a–a bond chain dominates anisotropic growth of LLM-105 crystal, while the solvent effect modulates edge energy and nucleation barrier. Notably, DMSO requires the highest supersaturation to trigger 2D nucleation, reflecting its stronger solvation of LLM-105 compared with NMP and DMF. These findings offer a molecular-level insight into supersaturation-regulated morphology and provide guidance for the design of energetic materials with tailored crystal shapes. This work aims to elucidate the effect of supersaturation on the crystal morphology of LLM-105 in three solvents, DMSO, NMP and DMF.